Was wondering if you checked your can resistance again after the ecm started not working again. The info you were looking at with your students said that communication would still work if one or both resistors failed. I have had engines that wound not communicate with a scan tool if one of the resistors was missing. Just a thought on what may have happened with the failed ecm, would also like to know if communication still would work without a resistor. I am off to watch the third video.
One other mention on the gm ecbm video. The can wiring schematic was very strange. What I mean by that is the can system I deal with it is a continuous circuit with each module along the way spliced into the circuit. The one you had looked like it piggybacked each module on one another.
